Safe words are phrases or a single word decided upon in a D/s relationship before a scene starts or any kinky activity is engaged in.
The most typical safe words you might here are Green, Yellow, Red. These are actually the safe words I use. Usually, the usage of these words are universal.
Green: Everything is fine. I'm okay. More.
Yellow: Slow down. Change what we're doing.
Red: Stop. I'm scared. I'm hurt. No more. End the scene. No.
Why not just say...